If the x=4, then its equivelent to 12 + 4, which equals 16.
20 - 4 = 16
4 x 4 = 16
16 = 1 x 16 = 2 x 8 = 4 x 4
20
1 x 16, 2 x 8, 4 x 4, 8 x 2, 16 x 1.
1 x 16, 2 x 8, 4 x 4, 8 x 2, 16 x 1 = 16
3x + 4 = 16 3x = 16 - 4 x = 12/3 x = 4
4x4 = 16 is a perfect square.
16
4
-3